1. Field of the Invention
This invention relates to a substrate processing apparatus and a method for manufacturing a semiconductor device, and is preferable particularly for a vertical apparatus for performing a batch process on a plurality of semiconductor substrates.
2. Description of the Related Art
A conventional reaction furnace of a vertical apparatus, for example, a furnace of double tube structure, includes an outer reaction tube and an inner reaction tube which are disposed coaxtially with each other An upper portion of the outer reaction tube is blocked and a lower portion of the outer reaction tube is opened, and both upper and lower portions of the inner reaction tube are opened The lower openings of the outer reaction furnace and the inner reaction furnace are connected a furnace opening flange which it provided with a gas introducing nozzle and a gas exhausting opening. A furnace opening of the furnace opening flange is covered with a seal cap which is provided at a lower portion of a boat inserted into the inner reaction tube. A number of wafers are loaded on the boat, and a batch process is performed on the wafers In a reaction atmosphere.
An interior of the reaction furnace is evacuated to vacuum, and then, a reaction gas is introduced through the gas introducing nozzle, and the reaction gas accompanied with an atmosphere within the lower portion of the furnace enters into the inner reaction tube, and flows upwardly while being In contact with a number of wafers loaded on the boat. In this case, the reaction gas is decomposed by heating the wafers, and the reaction product is deposited onto a surface of the wafers so as to form a film. After the processing, the gas is reversed at the upper portion of the outer reaction furnace, and then flows downwardly through a path defined between the outer reaction tube and the inner reaction tube so as to be exhausted from the lower portion of the furnace. Therefore, in the apparatus of double tube structure, the flow of the gas in the reaction atmosphere where the wafers exist Is from below to above.
In the seal cap for covering the above-mentioned furnace opening flange and the furnace opening, an O-ring for vacuum sealing is frequently used. Therefore, a component of the O-ring may be released from the O-ring in the form of a gas, or an outside atmosphere may get into a furnace by leakage from the sealing. Furthermore, in some apparatuses, a boat rotation mechanism for rotating a boat during film formation may be attached to a seal cap, therefore, the rotation mechanism may be another contamination source. These contamination sources are concentrated on a furnace opening portion at a lower portion of a reaction furnace. Accordingly, the furnace opening may be a contamination source for contaminating a reaction atmosphere.
In the above-mentioned reaction furnace of double tube structure, the contamination source of the furnace opening portion is located upstream of the flow of the gas in the reaction atmosphere where wafers exist. Therefore, the gas introduced from the lower portion reaches the wafers while containing the contaminant generated from the contamination source which is located in the upstream. As a result, the contaminant contained in the gas adheres to the wafers so that a haze which causes the film formation surface to cloud and the like are generated thereby leading to a cause of a poor film growth. Moreover, in a process such as an epitaxial growth and the like, which requires a highly clean reaction atmosphere, the above-mentioned contaminant may inhibit a process reaction and may hinder adhesion of a reaction gas thereby leading to a factor responsible for deterioration In doping amount uniformity.
In addition, the above-mentioned problem is also encountered In a reaction furnace of single tube structure. In some reaction furnaces of single tube structure without an inner reaction tube, a gas introducing nozzle is extended to an upper portion within a reaction tube, and a reaction gas is supplied from the upper portion to the lower portion and exhausted from the lower portion of the reaction tube. In this case, although a contaminant source will exist downstream of the gas, a contaminant at a furnace opening portion is whirled up when the gas is exhausted from the lower furnace portion so that the contaminant reaches wafers by reverse-diffusion thereby causing a similar problem as mentioned-above.
An object of the present invention is to provide a substrate processing apparatus and a method for manufacturing a semiconductor device wherewith, by resolving the problems with the prior art noted In the foregoing, a process in a highly clean atmosphere without contamination can be accomplished.
The invention of claim 1 resides in a substrate processing apparatus comprising: a furnace for processing at least a single substrate therein, with a furnace opening covered with a seal cap; a reverse-diffusion preventing body, provided between a substrate processing space and a furnace opening portion space at a side of the furnace opening, within the furnace, for preventing reverse-diffusion of a contaminant at the side of the furnace opening from the furnace opening portion space to the substrate processing space; a reaction gas introducing system for introducing a reaction gas into the furnace so as to process the substrate; a process exhausting system for exhausting the introduced reaction gas from substrate processing space; and a furnace opening exhausting system for exhausting the furnace opening portion space independently of the substrate processing space.
Since measures against contamination at the side of the furnace opening is designed in such a way that a reverse-diffusion preventing body is provided between a substrate processing space and a furnace opening portion space, and that the furnace opening portion space is exhausted independently of the substrate processing space, it is possible to effectively prevent reverse-diffusion of a contaminant from the furnace opening portion space to the substrate processing space.
The above-mentioned substrate processing apparatus includes a surface processing apparatus, a film formation apparatus, an epitaxial film formation apparatus, an SiGe film formation apparatus, and the like.
The invention of claim 2 resides in a substrate processing apparatus according to claim 1, comprising a purge gas Introducing system for purging an inside of the furnace opening portion space by supplying an inert gas such as N2 and the like, or H2 gas into the furnace opening portion space. The furnace opening portion space is exhausted while being purged by supplying an inert gas such as N2 and the like, or H2 gas into the furnace opening portion space, to thereby more effectively prevent reverse-diffusion of a contaminant.
The invention of claim 3 or 4 resides in a substrate processing apparatus according to claim 1 or 2, wherein a pressure of the furnace opening portion space is kept lower than a pressure of the substrate processing space. It is possible to still more effectively prevent reverse-diffusion of a contaminant by keeping a pressure of the furnace opening portion space lower than a pressure of the substrate processing space.
The invention of claims 5 through 8 resides in a substrate processing apparatus according to claims 1 through 4, respectively, wherein the reaction gas introducing system is configured to directly supply the reaction gas into the substrate processing space. Since the reaction gas is directly supplied into the substrate processing space so that the reaction gas does not allow a contaminant within the furnace opening portion space to be involved in the substrate processing space, it is possible to still more effectively prevent reverse-diffusion of a contaminant.
The invention of claims 9 through 16 resides in a substrate processing apparatus according to claims 1 through 8, respectively, wherein the process of the substrate is a process for forming an epitaxial film onto a substrate surface. The substrate processing apparatus of this invention is used preferably in the case that the substrate process is a film formation of an epitaxial film, and it is used, in particular, preferably in the case of a film formation of an SiGe film.
The invention of claim 17 resides in a method for manufacturing a semiconductor device, comprising the steps of: inserting at least a single semiconductor substrate into a furnace and covering a furnace opening with a seal cap; preventing reverse-diffusion of a contaminant at the furnace opening portion from a furnace opening portion space at the side of the furnace opening to a substrate processing space, within the furnace; introducing a reaction gas into the furnace so as to process the semiconductor substrate; exhausting the introduced gas, from the substrate processing space: and exhausting the furnace opening portion space independently of the substrate processing space.
According to this invention, since measures against contamination at the side of the furnace opening is designed to comprise the steps of; preventing reverse-diffusion of a contaminant from a furnace opening portion space to a substrate processing space; and exhausting the furnace opening portion space independently of the substrate processing space, it is possible to effectively prevent reverse-diffusion of a contaminant from the furnace opening area to the substrate processing space. The invention of claim 18 resides in a method for manufacturing a semiconductor device, according to claim 17. wherein the reaction gas is a gas for forming an SiGe film. A gas for forming an SiGe film is, for example, a mixed gas of monosilane (SiH4). monogermane (GeH4), monomethylsilane (CH3SiH3), diborane (B2H6) and hydrogen (H2).